linux-kernel - Re: [PATCH v1 2/2] dmaengine: idxd: fix potential NULL pointer dereference on wq setup error path

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Message-ID: <19668a72-c523-42ab-87ac-990a4baac214@intel.com>
Date: Thu, 22 May 2025 07:56:08 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Shuai Xue <xueshuai@...ux.alibaba.com>, vinicius.gomes@...el.com,
 fenghuay@...dia.com, vkoul@...nel.org
Cc: dmaengine@...r.kernel.org, colin.i.king@...il.com,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] dmaengine: idxd: fix potential NULL pointer
 dereference on wq setup error path



On 5/21/25 11:33 PM, Shuai Xue wrote:
> If wq allocation fails during the initial iteration of the loop,
> `conf_dev` is still NULL.  However, the existing error handling via
> `goto err` would attempt to call `put_device(conf_dev)`, leading to a
> NULL pointer dereference.
> 
> This issue occurs because there's no dedicated error label for the WQ
> allocation failure case, causing it to fall through to an incorrect
> error path.
> 
> Fix this by introducing a new error label `err_wq`, ensuring that we
> only invoke `put_device(conf_dev)` when `conf_dev` is valid.
> 
> Fixes: 3fd2f4bc010c ("dmaengine: idxd: fix memory leak in error handling path of idxd_setup_wqs")
> Cc: stable@...r.kernel.org
> Reported-by: Colin King <colin.i.king@...il.com>
> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> ---
>  drivers/dma/idxd/init.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index 760b7d81fcd8..bf57ad30d613 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -196,7 +196,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
>  		wq = kzalloc_node(sizeof(*wq), GFP_KERNEL, dev_to_node(dev));
>  		if (!wq) {
>  			rc = -ENOMEM;
> -			goto err;
> +			goto err_wq;
>  		}
>  
>  		idxd_dev_set_type(&wq->idxd_dev, IDXD_DEV_WQ);
> @@ -246,6 +246,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
>  	put_device(conf_dev);
>  	kfree(wq);
>  
> +err_wq:
>  	while (--i >= 0) {
>  		wq = idxd->wqs[i];
>  		if (idxd->hw.wq_cap.op_config)